Discuss the parity selection rule for electric dipole transitions of a single-electron atom (the Laporte rule). The electric dipole matrix element is \(\left\langle n^{\prime} l^{\prime} m^{\prime}|\boldsymbol{r}| n l m\rightangle\), where \(\boldsymbol{r}\) is the coordinate operator, \(n\) is a principal quantum number, and \((l, m)\) are angular momentum quantum numbers.